gevent 1.5.0 specifies a cython file as a prerequisite, causing cython to run only when it was installed after 2020

[haampie]

When installing spack install py-gevent it resolves to

py-gevent@1.5.0
    py-cffi@1.15.1
        libffi@3.4.4
        py-pycparser@2.21
    py-cython@0.29.33
    py-greenlet@1.1.3
    py-pip@23.0
    py-setuptools@63.0.0
    py-wheel@0.37.1
    python@3.10.8
    ...

and attempts a build using pypi tarballs.

Description:

py-gevent re-cythonizes files because it has a prereq specified on cython files:

Compiling src/gevent/resolver/cares.pyx because it depends on /opt/linux-ubuntu20.04-x86_64/gcc-11.1.0/py-cython-0.29.32-wistmswtv7bm55wpadctrr3eqb7jnona/lib/python3.10/site-packages/Cython/Includes/libc/string.pxd.

So, depending on what date you've installed cython on your system, it runs cython or not.

It's like writing a makefile that specifies a system library as a prereq by absolute path...

Also, is there a way to tell gevent setup that it should always run cython no matter what?

[jamadden]

gevent 1.5 is quite old and no longer supported by this project. But here are some things I remember.

gevent does not specify a dependency on string.pxd; that's simply how cython works.

If cython is installed at setup/build time, cython will be run. If it is not installed, the bundled C files will be used. It's as simple as that.

Except it's not quite that simple. gevent 1.5 was the first release to include a pyproject.toml, which was a relatively new thing at the time, and many users were using build systems that did not pay attention to it. Those that do, however, will fetch a released version of cython at build time, and cythonize any necessary files. This is the only way we could have a hope of running on newer versions of CPython, as the generated C files only support releases that were available at the time it was created.

[haampie]

If cython is installed at setup/build time, cython will be run. If it is not installed, the bundled C files will be used. It's as simple as that.

That doesn't happen... cython only runs when its files have a newer mtime than the source files of gevent; that's rather absurd. It's causing build failures because apparently the version of cython that was used at the time of gevent 1.5.0 was too old to support Python 3.10.8.

Should I open an issue with cython about that mtime problem then? It looks like you expect cython to always run when it's in the PATH. Or is there a flag that forces a re-make, like make --always-make

[jamadden]

cython only runs when its files have a newer mtime than the source files of gevent

No, cython always runs. Whether it does anything or not is up to it, and out of control of this project.

[haampie]

It is not out of control of the project, since cythonize(..., force=True) can be used to avoid the mtime checks, which
makes sense for releases (and not for development).

[jamadden]

I meant it is way out of gevent 1.5's control. That ship sailed long ago.